Despite our increased understanding of the determinants of substance abuse, the treatment of addictive disorders continues to be a major public health problem. Substantial evidence documents the importance of ethno-cultural factors in the phenomenology, course, and treatment of substance use disorders (SUD). A better understanding of the role of ethnicity and acculturation in substance use treatment and prevention is particularly necessary among Hispanics, who are the largest minority group in the US. A deeper understanding of SUD among Hispanics is urgently needed to promote the well-being of this rapidly growing and chronically underserved minority group. While the role of Hispanic ethnicity in the risk for SUD and rates of treatment utilization is well established, little is known about the mechanisms underlying these effects. We draw on concepts from cultural and immigration studies, epidemiology and social psychiatry to examine the potential mediating mechanisms of the ethnic variation in the onset, course, and treatment of SUD. We propose to use data from the NESARC, a large national survey of substance use and other psychiatric disorders (conducted in 2002 with follow-up in 2005) that included 43,093 respondents and oversampled for Hispanics. The NESARC included detailed information on substance use and SUD, associated psychopathology and a broad array of risk factors. It also included 15 measures capturing different dimensions of acculturation, allowing for the detailed modeling of three integrated theoretical perspectives: Berry's model of acculturation, segmented assimilation, and Andersen's Behavioral Model of Services Use. This study will provide us with a unique opportunity to obtain information on the effect of Hispanic ethnicity and acculturation patterns on the etiology, course, and treatment-seeking patterns of individuals suffering from SUD. The models derived from our investigation will have the potential to serve as the basis for developing empirically-informed interventions to improve prevention and treatment of SUD in Hispanics.